@lanodan @alyx @isa @jonossaseuraava it depends, soviet metro used several different versions of the PA system, some I think used radio where station would broadcast PA announcement to train as it arrives, but most later ones were different forms of casette tape like devices, from actual casette tapes to glorified mp3 players.
Metro train most often does not know where it is on the line, those systems are a bit rare. Remember that trains have more electrics than they do electronics, and they date to 1940s-1950s, transistors weren't widespread back then, so "where i am on the line" system just wasn't possible, i mean the best and most widespread system that IS put into place is speed regulation, which lets train know "what speed limit is on this segment", and that only happened around 1960s.
I guess some systems like st. petersburg metro does have this advanced stuff like letting train know where it is, auto-drive for precise stopping (for "horizontal elevator" type stations) and stuff, but those are more of an exception than rule. Only in recent years (2010s?) they added a (better) precise stopping electronics system.
Hey if you have 30GiB+ to spare you can try jank ass gmod metro simulator on my server
https://ebin.club/site/garrys-mod-servers/image.png